Long time lurker, first time poster!
Went to Officeworks today to grab a Western Digital My Passport Essential 500GB for $129 (as per http://www.ozbargain.com.au/node/19131) and it appears they have now discontinued the 500GB model and replaced it with the Western Digital My Passport Essential SE 640GB for the same price.
Decent price for any 640GB 2.5" portable hard drive, but an exceptional price for this model in my opinion.
Also for those who don't need a 640GB and interested for a smaller capacity 2.5" portable hard drive, I noticed that Harvey Norman have on clearance the Western Digital Elements 320GB for $78.
Being fussy I know, but the shape isn't as nice as the older version